Hoist control



April 15, 1941- J. E. BORLAND HOIST CONTROL Filed Feb. 20, 1940 a m n 2WW W? 7 I 0 I w m 6 M B 5 m 7 4 m 3 r3 F E 2 M 4 4 am s 0 KW Z w m5 m 39 z a a J 4 2 L L Mu Z 73% W. w

BY M ATTORNEY Patented Apr. 15, 1941 HOIST CONTROL James E. Borland,Pittsburgh, Pa., assignor to Westinghouse Electric & ManufacturingCompany, East Pittsburgh, Pa., a. corporation of PennsylvaniaApplication February 20, 1940, Serial No. 319,873

Claims.

My invention relates to a control system which is particularly useful inmine hoists and the like.

In the control for motors operating mine hoists, and the like, it iscommon practice to provide limit switches for protectionagainstoverwind, or overtravel of a skip or cage, either at the top ofthe shaft (in the head frame) or at the bottom of the shaft. It is alsocommon practice to provide, in the control, a device, ordinarily knownas a back-out switch, to permit the operator to short-circuit theovertravel limit switch (or switches) that have been opened, and at thesame time disconnect the control circuits to one set of reversingcontactors, so that power can be applied to the hoist only in adirection to back out of the overwind.

Such protective devices as have been employed in the past do not givefull protection, for, with a balanced hoist (employing twointerconnected skips or cages in separate shaft compartments) after anoverwind, if the operator should move the back-out switch in a directionto short-circuit the limit switch that has opened, and then release thebrakes, it is possible for the skip or cage in the head frame to bemoved farther in the direction of overwind, under the overhauling loadof the rope and skip (or cage) in the other shaft compartment. Also, toobtain power for backing out of the overwind, it is necessary for theoperator to move the master switch in the pro-per direction. If he movesthe master switch in a direction that would normally apply power in adirection to continue the overwind, the circuit to the reversingcontactors would be broken on the master switch, so that power would notbe applied. This, of course, would give the same results as would beobtained by releasing the brake without moving the master switch, andunder the overhauling load, the skip or cage may be pulled farther inthe overwind direction, with consequent damage, unless the operator actsquickly enough to reapply the brake.

An object of my invention is to provide a control scheme which will makeit impossible, after overtravel of the skips, to release the brakes ifpower is applied in the wrong direction, that is,-

in a direction to cause farther overtravel (or overwind).

Another object of my invention is to provide a control scheme which,after overtravel of the tion when considered in conjunction with the ac-1 companying drawing, in which the single figure is a schematic showingof a control system embodying the principles of my invention.

Referring more particularly to the single figure, numerals l and 2denote skips or cages which are suspended by cables 3 and 4, wound ondrums 5 and 6, respectively. The two drums 5 and 6 are mechanicallycoupled by a brake drum 1 through shafts 8 and 9 or through suitableclutches (not shown) if desired. A driving motor In has an armature Hwhich is mechanically coupled through gears 12 to drums 5 and 6(assuming the clutches, if utilized, are engaged). The speed of motorIt] may be varied by varying resistor l3 which will change the value ofcurrent through field winding I4. Energy is supplied to motor Ill bygenerator I5 which has an armature l6 connected across the terminals ofmotor armature l l. Variable resistors I 1 change the value of currentthrough field winding [8, thereby securing different values ofgenerating current. Reversing contactors l9 and are provided in order tosecure reversal of current flow through field winding l8, therebysecuring reversal of motor Ill.

The operation of the control system is as follows:

Assume that the control system is in a deenergized condition as shown inthe drawing and assume that it is desired to hoist the left skip l. Theoperator will thus move controller 2| to the left and by means of itscontact segments will bridge contact members 22, 23 and 24--contactmember 22 being considered also as a positive terminal of a directcurrent source of potential. A circuit will now be completed through allthe limit switches 2'5, 26, 21 and 28 and through actuating coil 29 ofrelay 30 which may be traced from the terminal 22 through the controllersegment and contact member 24, through conductors 3|, 32, limit switches26, 28, 25 and 21, (in the order named) conductors 33 and 34, actuatingcoil 29 to the negative terminal 35 of the direct current source.Energization of coil 29 will cause relay 30 to close contact members 36,31 and 38.

Closing of contact members 36 will complete a circuit from the terminalmarked immediately adjacent thereto, through contact members 36,conductor 39, thence through two parallel circuits, one going throughbrake coil 40 of the auxiliary or emergency brake 4| to a negativeterminal and the other going through brake coil 42 of the emergencybrake 43 to a negative terminal. Energization of both brake coils 40 and42 will counteract the force of the associated brake-applying springs 44and 45, respectively, and release the brakes. In order to fully releasethe drums a mechanically operated brake 46 must also be released.

Since, as described above, contact members 3'! are closed, anothercircuit will be completed from the terminal 22, through contact members22, 23 and 31, the actuating coil of reversing contactor I9 to theterminal, thus actuating contactor l9 and completing a circuit fromterminal 41, through contact members 48, resistor 11, generator fieldwinding I8, contact members 49 to the terminal marked Now since thegenerator field winding I8 is energized, motor it will be driven in adirection so as to raise the left skip I. Still another circuit will becompleted which may be traced from terminal 22 through the controllersegment and contact members 23, through conductor 55, the actuating coili of relay 52 to the terminal. Actuation of relay 52 will at this stagehave no effect on the system however.

Assume now that the left skip, either through neglect of the operator orfor any other reason, has been hoisted too far, thus effecting openingof limit switches 25 and 2'! by virtue of the screw propelled, switchoperating members 5353a and 54-54(1 forming a carriage as is well knownin the art. Opening of limit switches 25 and 2'! will, of course,interrupt the first mentioned circuit through all the limit switches andactuating coil 29 thereby effecting deenergization of relay and openingof contact members 36, 3'! and 38. Opening of contact members 36 willdeenergize brake coils 40 and 42 and effect application. of the brakesby springs 44 and 45 (or any other suitable means such as hydraulicmeans or compressed air). Opening of contact members 3'! will effectdeenergization of relay 52 and of contactor 15, the latter eifectingdeenergization of the generator field winding l3 thus stopping motor In.

In order to restore skips I and 2 in a nonoverwound or non-overtravelledposition, a back out switch 55 is thrown to the right thus bridgingcontact members 56. Mechanical brake 45, if previously applied, is nowreleased. Now controller 21 is moved to the right in order to raise theright skip 2 and lower the left skip I so as to remove them from theiroverwound position.

A circuit will now be completed extending from terminal 22, through theleft controller segment, contact members 51, conductor 58, the coil ofrelay 59 to the terminal thereby effecting closing of contact members65.

Another circuit will now be completed through limit switches 26 and 28and actuating coil 25 which may be traced from the terminal 22 throughthe left controller segment, contact member 24, conductors 5| and 32,limit switches 25 and 28, conductors 5!, 62 and 63, contact membars 55,conductor 55, contact members 58, conductors 5'! and 34, coil 29 to theterminal 35. Energization of coil 29 will actuate relay 30 so as toclose contact members 35, 31 and 38 so as to restart the motor. However,reversing contactor 25, instead of reversing contactor I9 will beenergized (due to the movement of controller 2| to the right) therebyreversing the current through generator field coil I8 thereby effectingreversal of motor I 5 and effecting a drive in an opposite direction tothat previously described above so as to cause raising of the right skip2 and lowering of the left skip so as to Withdraw the skips from, theirovertravelled position.

Let us assume instead that the operator, after having thrown the backoutswitch 55 to the right, that, by mistake, he moves controller 2| to theleft instead of the right thereby tending to raise the left skip andlower the right skip thereby causing further overtravel or furthermovement into the overwind. In doing so, relay 52 instead of relay 59will become energized consequently contact members 68 will close butcontact members 60 will open. Opening of contact members 50 willinterrupt the last described circuit extending through limit switches 25and 28 and coil 25. It is true that while mechanical brake :55 isapplied a temporary shunt path will be formed across contact member 63by virtue of the closed brake contact members 59 operated thereby,however, this path will become immediately opened as soon as the lever10 is operated so as to release the mechanical brake 46.

In other Words, the limit switches are nullified by virtue of a shuntpath only if contact members 65 and contact members 68 are both closedsince both of these contact members are in series in the shunt path,hence both must be closed to complete it, However, if either contactmembers 55 (due to wrong movement of controller 25) or contact members(58 are open (due to wrong movement of the backout switch 55), then noshunt path will be formed to effect bridging of limit switches 25 and 21hence the brakes cannot be released.

Similarly as described above, if the left skip should descend too lowand the right skip, too high, limit switches 25 and 28 would openthereby stopping the drive. Thereafter, in order to move the skips outof the overwind, it will be necessary to throw backout switch 55 to theleft to close contact members H, and to move controller 26 to the leftso as to effect closing of contact members 58. Contact members H and 53are series connected and when they are both closed form a shunting pathacross limit switches 25 and 28 so as to permit operation of motor it soas to remove skip from their overwoundpositions. Brake contact members15 form a shunt path across contact members 68 only when the mechanicalbrake is applied and not when it is released.

Although two limit switches 25 and 2'! operate as the result ofexcessive hoisting of left skip I and excessive lowering of right skip2, it will be readily apparent that a single limit switch could be usedinstead to denote both of these conditions. Likewise a single limitswitch could be used instead of limit switches 26 and 28 to denoteexcessive lowering of the left skip as well as excessive hoisting of theright skip. By using two limit switches as shown in the drawing insteadof one there may be a time delay between the operation of one and theoperation of the other thus permitting a more flexible scheme.

I am, of course, aware that others, particularly after having had thebenefit of the teachings of my invention, may devise other devicesembodying my invention, and I, therefore, do not wish to be limited tothe specific showings made in the drawing and the descriptive disclosurehereinbefore made, but wish to be limited only by the scope of theappended claims and su h prior art that may be pertinent.

I claim as my invention:

1. A control system including a reciprocable element, a motor forreciprocating said element within a predetermined path, a brake limitswitch means which is operable when said element overtravels saidpredetermined path to apply said brake, back-out switch means forrendering ineffective said first-mentioned means connected in shuntrelationship with said limit switch means, for releasing said brake, andfor allowing application of power from said motor to said element forreturning said element from its overtravelled position to a position insaid predetermined path, and means dependent upon the occurrence ofovertravel of said reciprocable element and the direction of power flowto said motor for making said releasing of said brake impossible in theevent of application of motor power to said element which would tend tocause further overtravel instead of return to said predetermined path.

2. A control system including a reciprocable element, a motor forreciprocating said element within a predetermined path, a brake, limitswitch means which is openable when said element overtravels saidpredetermined path to apply said brake, back-out switch means connectedin shunt relationship with said limit switch means for renderingineffective said limit switch means for releasing said brake, and forallowing application of power from said motor to said element forreturning said element from its overtravelled position to a position insaid predetermined path, and means dependent upon the occurrence ofovertravel of said reciprocable element and the direction of power flowto said motor for making said releasing of said brake impossible in theevent of application of motor power to said element which would tend tocause further overtravel instead of return to said predetermined path.

3. A control system including a reciprocable element, a motor forreciprocating said element within a predetermined path, a brake, limitswitch means which is operable when said element overtravels saidpredetermined path to apply said brake, back-out switch means connectedin shunt relationship with respect to said limit switch means forrenderin ineffective said limit switch means connected in shuntrelationship with said limit switch means, for releasing said brake, andfor allowing application of power from said motor to said element forreturning said element from its overtravelled position to a position insaid predetermined path, and means dependent upon the occurrence ofovertravel of said reciprocable element and the direction of power flowto said motor for making said releasing of said brake impossible in theevent of application of motor power to said element which would tend tocause further overtravel instead of return to said predetermined path.

4. A control system including a pair of skips or cages connected forbalanced operation, that is, which are simultaneously reciprocable inopposite directions, a reversible motor for so reciprocating said skips,a brake limit switch means associated with each skip which is operablewhen the skip goes too high or too low with respect to a predeterminednormal path, back-out switch means for rendering ineffective said limitswitch means connected in shunt relationship with said limit switchmeans, for releasing said brake, and for allowing application of powerfrom said motor to said skips for returning said skips from theirovertravelled position to a position in said predetermined path, andmeans dependent upon the occurrence of overtravel of said reciprocablecages and the direction of power flow to said motor for making saidreleasing of said brake impossible in the event of application of motorpower to said skips which would tend to cause further overtravel insteadof return to said predetermined path.

5. A control system including a pair of skips or cages connected forbalanced operation, that is, which are simultaneously reciprocable inopposite directions, a reversible motor for so reciprocating said skips,a pair of limit switch means, one of which is openable to apply saidbrake when aparticular skip goes too high, and the other of which isalso openable to apply'said brake when the same skip goes too low withrespect to a predetermined normal path of movement, a pair of manuallyoperable back-out switch means each of which is connected in shuntrelationship with one of said limit switch means for renderingineffective one of said limit switch means after it has operated becauseof overtravel of the skips, to allow release of said brake andapplication of motorpower to said skips for their return to saidpredetermined normal path, a master controller for effecting reversingoperation of said motor, a pair of auxiliary contactors which arerespectively operable by opposite movements of said master controller,one to effect hoisting of one skip and lowering of the other and theother to effect opposite movement of both skips, circuit meansinterconnecting said back-out switches, auxiliary contactors and limitswitch means and dependent jointly upon the direction of overtravel ofthe skips and the direction of movement of the master controller toprevent release of said brake in the event said master controller ismoved in the wrong direction after overtravel, that is in a direction tocause further overtravel instead of return to said predetermined normalpath. I

6. A control system including a pair of skips or cages connected forbalanced operation, that is, which are simultaneously reciprocable inopposite directions, a reversible motor for so re- 7 ciprocating saidskips, a pair of limit switch means, one of which is operable to applysaid brake when a particular skip goes too high, and the other of whichis also operable to apply said brake when the same skip goes too lowwith respect to a predetermined normal path of movement, a pair ofback-out switch means each of which is for rendering ineffective one ofsaid limit switch means connected in shunt relationship with one of saidlimit switch means, to allow release of said brake and application ofmotor power to said skips for their return to said predetermined normalpath, a master controller ior eifecting reversing operation of saidmotor, a pair of auxiliary contactors which are respectively operable byopposite movements of said master controller, one to effect hoisting ofone skip and lowering of the other and the other to effect oppositemovement of both skips, said back-out switches and said auxiliarycontactors being connected in series relationship, each back-out switchtogether with one of said auxiliary contactors forming a shunt pathacross one of said limit switch means so as to prevent release of saidbrake in the event said master controller is moved in the wrongdirection after overtravel,

that is in a direction to cause further overtravel instead of return tosaid predetermined normal path.

7, A control system including a pair 01' skips or cages connectedforbalanced operation, that is, which are simultaneously reciprocable inopposite directions, a reversible motor for so reciprocating said skips,a pair of limit switch means, one of which is operable to apply saidbrake when a particular skip goes too high, and the other of which isalso operable to apply said brake when the same skip goes too low withrespect to a predetermined normal path of movement, a pair of back-outswitch means each of which is for rendering inefiective one of saidlimit switch means connected in shunt relationship with one of saidlimit switch means, to allow release of said brake and application ofmotor power to said skips for their return to said predetermined nor- 1mal path, a master controller for eifecting reversing operation of saidmotor, a pair of auxiliary contactors which are respectively operable byopposite movements of said master controller,

one to eifect hoisting of one skip and lowering actuating coil, each ofsaid brake contactors bea ing connected in shunt relationship with oneof said auxiliary contactors, a master controller for effecting controlof said reversible motor and movement of which, on either side of aneutral position, is effective to close one of said auxiliary Icontactors thereby allowing release of said brake only on condition thatsaid master controller is moved in the proper direction to close theproper auxiliary contactor, after overt-ravel of skips, for restoringthem to said predetermined normal path.

8. A control system including a pair of skips or cages connected forbalanced operation, that is, which are simultaneously reciprocable inopposite directions, a reversible motor for so reciprocating said skips,a brake limit switch means associated with each skip which is operablewhen the skip goes too high or too low with respect to a predeterminednormal path, a pair of backout switches, a pair of brake contactors anda brake actuating coil all connected in series circuit relationship, apair of limit switches, each of which bridges one back-out switch andone serially connected aforementioned brake contactor, means dependentupon the direction of overtravel of the skips and the direction ofenergy application to said reversible motor for opening said brakecontactors and for making it impossible to energize said brake actuatingcoil to reiii lease the brake in the event said application ofmotivating energy is applied in the wrong direction to effect back-outof said skips, following overtravel thereof.

9. A control system including a pair of skips or cages connected forbalanced operation, that is, which are simultaneously reciprocable inopposite directions, a reversible motor for so reciprocating said skips,a brake limit switch means associated with each ski which is operablewhen the skip goes too high or too low with respect to a predeterminednormal path, a manually operable double-throw switch device including apair of back-out switches, a pair of brake contactors and a brakeactuating coil all connected in series circuit relationship, a pair oflimit switches, each of which bridges one back-out switch and oneserially connected brake contacto-r, mechanical brake releasing meansfor opening said brake contactors, and an auxiliary con tactor in shuntrelationship with each of said brake contactors and which areselectively energized depending upon the direction of drive imposed onsaid skips by said motor and which are eflective either to allow or notto allow release of said brakes depending upon whether or not the properdirection of drive has been imposed on said skips, following overtravelthereof, to return them to said predetermined normal path.

10. A control system including a pair of skips or cages connected forbalanced operation, that is, which are simultaneously reciprocable inopposite directions, a reversible motor for so reciprocating said skips,a brake limit switch means associated with each skip which is operablewhen the skip goes too high or too low with respect to a predeterminednormal path, a pair of backout switches, a pair of brake contactors anda brake actuating coil all connected in series circuit relationship, apair of limit switches, each of which bridges one back-out switch andone serially connected brake contactor, means for opening said brakecontactors, and an auxiliary contactor in shunt relationship with eachof said brake contactors, a master controller controlling the directionof rotation of said motor, said auxiliary contactors being openable bysaid master controller so that movement of said master controller foreffecting either forward or reverse drive will close only one of saidauxiliary contactors, thereby effecting release of said brake providedthat the master controller is moved in the proper direction, followingovertravel of the skips, to return the skips to said predeterminednormal path, and to prevent release thereof in the event of movement ofthe controller in a direction which would tend to cause furtherovertravel.

JAMES E. BORLAND.

